1. Field of the Invention
The present invention relates to a portable electronic apparatus, known as an Integrated Circuit Card (IC Card), which incorporates an IC chip having, e.g., a nonvolatile memory and a control element such as a CPU and, more particularly, to a portable electronic apparatus in which an access control method for an area of the memory is improved.
2. Description of the Related Art
A so-called IC card which incorporates an IC chip having, e.g., a nonvolatile memory and a control element such as a CPU has been developed as a portable storage medium. An IC card of this type as disclosed in U.S. Pat. No. 4,988,855 inventor of which is same as present invention, stores an identification number as key data in its internal memory. When an identification number is externally input, it is collated with the registered identification number stored in the memory, and subsequent memory access is enabled or disabled in accordance with the collation result.
In the conventional IC card, the collation result continues to be held at all times during the power supply to the IC card. If, in this case, an authorized person makes a key data collation for example, a corresponding collation result is held during a period of time in which the IC card is inserted. If, on the other hand, any unauthorized person gains access to the IC card, by some method, during an intervening period of time, it is not possible at all to prevent any unauthorized access to the IC card data.